Prosthetic heart valve having a pair of support rings of dissimilar material

ABSTRACT

A prosthetic heart valve having an inner support ring of rigid non-thrombogenic material and a malleable metallic outer support ring positioned about the periphery of the inner ring and bent into the immovable clamping relationship therewith. A portion of a tubular fabric member is retained between the two clamped rings, and the remainder of the fabric member is folded into a plurality of layers about the periphery of the outer ring to form a suturing site. Typically, the outer ring carries an outwardly extending flange on one side, which is overlaid by a single thickness of the tubular fabric, to hold the multiple layer suturing site away from the orifice of the inner ring.

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United States Patent Cromie [54] PROSTHETIC HEART VALVE HAVING A PAIR OFSUPPORT RINGS OF DISSIMILAR MATERIAL [72] Inventor: Harry W. Cromie,Pittsburgh, Pa.

[73] Assignee: Baxter Laboratories, Inc., Morton Grove,lll.

[22] Filed: May 7, 1971 [21] Appl.No.: 147,275

[151 3,691,567 51 Sept. 19, 1972 Attorney-W. Garrettson Ellis [5 7]ABSTRACT A prosthetic heart valve having an inner support ring of rigidnon-thrombogenic material and a malleable metallic outer support ringpositioned about the periphery of the inner ring and bent into theimmovable clamping relationship therewith. A portion of a tubular fabricmember is retained between the two clamped rings, and the remainder ofthe fabric member is folded into a plurality of layers about theperipheryof the outer ring to form a suturing site. Typically, the outerring carries an outwardly extending flange on one side, which isoverlaid by a single thickness of the tubular fabric, to hold themultiple layer suturing site away from the orifice of the inner rmg.

9 Claims, 4 Drawing Figures PATENTEDSEP 19 I972 3,591, 557

sum 2 IF 2 fizueizior H6027 W Cram 6'6 PROSTI-IETIC HEART VALVE HAVING APAIR OF SUPPORT RINGS OF DISSIMILAR MATERIAL BACKGROUND OF THE INVENTIONA need exists in the field of heart valve prostheses for valves whichwill not exhibit a build-up of clotted blood and fibrin during long termusage. A particularly sensitive area for the build-up of undesirablematerials is the ring orifice of the valve through which the bloodpasses when the orifice is not occluded by the moveable closure member.

It has been suggested in U.S. Pat. No. 3,526,005 that pyrolytic carbonis a particularly excellent coating for medical protheses. Similarly, itis suggested to use carbon parts for heat valves 'in U.S. Pat. No.3,526,906. Such materials exhibit a very low tendency to build upundesirable incrustations after implantation in a patient.

However, difficulties have been encountered in the effective design ofheat valves in which the blood orifice is made of carbon or anothernon-malleable, brittle material because of problems in assembling areliable,strong valve. The brittleness of carbon orthe like prevents theuse of the best conventional methods of valve fabrication developed foruse with malleable metal orifice rings.

Furthermore, when a suturing ring of the type disclosed by the priorart, for example U.S. Pat. Nos. 3,099,0l6 or 3,416,159, is used inconjunction with the heart valve, there is a danger that the surgeon mayemplace suture stitches very close to the orifice of the valve. Afterimplantation, these stitched sutures may enlarge or move, and interferewith the action of the movable closure member. This may result in ahazardous malfunction of the heart valve.

The heart valve of this invention provides an improved solution to theabove problems, in that a valve is provided which can carry a rigidvalve orifice assembly, so that the valve orifice can be fabricated fromthe most desirable formulations of non-thrombogenic carbon or ceramic,while the valve orifice assemble remains reliable mounted within anouter suturing ring. Additionally, the suturing ring of the valve ofthis invention can be held away from the valve orifice in a manner toreduce the risk of the sutures interfering with the action of themoveable closure member.

DESCRIPTION OF THE INVENTION In the drawing,

FIG. 1 is a perspective view of a prosthetic aortic heart valveconstructed in accordance with this invention.

FIG. 2 is a perspective view of the same valve with portions of thevalve broken away for purposes of clarity.

FIG. 3 is a partial magnified, sectional view of the valve rings andrelated parts of the valve of FIG. 1 shown in greater detail.

FIG. 4 is an exploded view of the major components of the valve of FIG.1 prior to assembly, omitting the tubular fabric member which is used asa suturing ring.

Referring to the drawings, a prosthetic heart valve is shown whichcomprises an inner support ring 10 of rigid non-thrombogenic material.Inner ring 10 defines a closure member 16 therein within said cage andmoveable between a position occluding flow through the orifice 18 of theinner ring and an open, flow permitting position.

Malleable metallic outer support ring 20 is positioned about theperiphery of inner ring 10, and has a plurality of spaced fingers 22positioned transversely to the plane of outer ring 20. As the valve isassembled, fingers 22 are bent about protrusion 12 to affix outer ring20 in immovable clamping relation with inner ring A folded tubularfabric member 24 has a portion thereof 26 clamped between inner ring 10and outer ring 20 as shown in FIG. 3. Other portions of the tubularfabric member are folded into a plurality of layers 28 about theperiphery of outer ring 20 to form a suturing site.

Typically, outer ring 20 carries an outwardly extending flange 30 on theside of said ring adjacent the clo sure member 16. Flange 30 is overlaidby a single thickness 32 of the tubular fabric 24. The purpose of flange30 is to underlie this thickness of tubular fabric to cause thefabric'immediately adjacent to inner ring 10 to be unsuitable as asuturing site, since a surgeon typically requires several layers offabric in order to ob.- tain reliable suturing of the valve to the hearttissue at the emplacement site. Also, flange 30 holds the folded layers28 of tubular fabric portion 24'away from the suturing site to reducethe risk that sutures will get too near the valve orifice, and interferewith the action of moveable closure member 16.

Referring in more detail to the parts already mentioned, inner ring l0ispreferably madeof a graphite substrate 34 of approximately 10 milsthickness, coated with a layer of isotropic pyrolytic carbon 36 ofapproximately 20 mils thickness, manufactured, for example, inaccordance with the teachings of U.S. Pat. No. 3,526,005. Alternatively,inner ring 10 can be made of a non-thrombogen'ic ceramic formulation,polytetraflouroethylene, or other non-thrombogenic plastic materials, ifdesired. The invention finds particular use in utilizing a rigid or evenbrittle inner support ring 10 having optimum non-thrombogeniccharacteristics, while the remainder of the valve is clamped to innerring 10 through the action of outer metallic ring 20. It is alsoadvantageous that outer ring 20 and inner ring 10 are not in contactwith each other, but are separated by a layer 26 of fabric, whichprotects inner ring 10 from cracking or chipping during themanufacturing operation. I

Closure member 16 is disclosed as a ball, typically hollow and made ofcarbon such as graphite with a pyrolytic carbon outer coating. Ifdesired, the pyrolytic carbon coatings used on ring 10 and closuremember 16 may contain a minor amount of silicon toincrease the strengthof the material. Alternatively, a ceramic or plastic ball can be used,or other known closure mem' bers such as pivoting or reciprocatingdiscs, poppet valves connected to a projectingneck and slidably held ina retention ring, or the like.

The valve of this invention is typically assembled by positioning theclosure member 16 and cage 14 with each strut of cage 14 passing througha cut away portion 38 in outer ring 20, and the horizontal portions40 ofcage 14 resting on protrusion 12 of inner ring 10.

Cage 14 can be made of titanium optionally coated withpolytetrafluoroethylene, carbon, or the like. Tubular fabric 24, inunfolded tubular position, is placed about inner ring 10, and outer ring20 is in turn placed about inner ring and fabric 24. Then fingers 22 ofouter ring are bent inwardly to the position shown in FIG. 3 to clampfabric tube 24 and cage 14. to inner ring 10.

Fabric tube 24 is typically made of dacron velour, or any other sturdy,desirable fabric.

Following the clamping of fingers 22, the two tubular sections of fabrictube 24 extending outwardly from the clamped rings 10, 20 on differentsides thereof are folded together about rings 10, 20, and thin retainerring 41, in the manner indicated in FIG. 3, and sewn about the entireperiphery of the valve along circular seams 42, 44 to retain the fabricin its folded position as a suturing ring. An additional, separate ringof fabric 46 can be added to the folded composite to provide extra bulkto the suturing ring if desired.

In the assembled valve, inner ring 10 presents to closure member 16 aconvex curved surface 48 along the vertical dimension, whereby a linecontact between the closure member and inner ring 10 is effected whenclosure member 16 is in flow occluding position as shown in FIG. 3.

The completed heart valve is sterilized in an autoclave or gassterilized with ethylene oxide, and prepared for suturing into theincision site.

Mitral or aortic valves can be constructed in accordance with thisinvention, having a valve orifice of rigid non-thrombogenic materialwhich is securely held together with a malleable clamping ring, and inwhich the fabric suturing ring is prevented from interfering with theaction of the closure member.

The above disclosure is for illustrative purposes only, and is not to beconsidered as limiting the invention of this application, which isdefined in the claims below.

That which is claimed is:

l. A prosthetic heart valve which comprises an inner support ring ofrigid, nonthrombogenic material, said inner ring defining an annularprotrusion about its periphery; a closure member retained adjacent saidinner ring and movable between a position occluding flow through saidinner ring and an open, flow-permitting position; a malleable metallicouter support ring positioned about the periphery of said inner ring andhaving a plurality of fingers which are bent about said protrusion toaffix said outer ring in immovable, clamping relation with said innerring; a tubular fabric member, a portion of which is clamped betweensaid inner and outer rings, other portions of said tubular fabric memberbeing folded into a plurality of layers about the periphery of saidouter ring to form a suturing site.

2. The valve of claim 1 in which said inner ring is made of carbon.

3. The valve of claim 2 in which said inner ring has an outer coating ofan isotropic pyrolytic carbon.

4. The valve of claim 1 in which said outer ring carries an outwardlyextending flange on a side of said ring adjacent said closure member,said flange being overlaid by a single thickness of tubular fabric, tocause fabric immediately adjacent the inner ring to be unsuitable as asuturing site, and to hold the folded tubular fabric portions away fromthe inner ring.

5. The valve of claim 4 in which said closure member is a hollow ball.

6. The valve of claim 5 in which said ball is made of carbon.

7. The valve of claim 5 in which the inner ring presents a convex curvedsurface along one dimension to said hollow ball, whereby a line contactbetween the ball and inner ring is effected when said ball is in flowoccluding position.

8. The valve of claim 7 having a cage for retaining said ball, said cagecomprising struts which rest on said protrusion and which are retainedbetween said inner and outer rings.

9. The valve of claim 8 in which both said inner ring and ball have anouter coating of an isotropic pyrolytic carbon.

2. The valve of claim 1 in which said inner ring is made of carbon. 3.The valve of claim 2 in which said inner ring has an outer coating of anisotropic pyrolytic carbon.
 4. The valve of claim 1 in which said outerring carries an outwardly extending flange on a side of said ringadjacent said closure member, said flange being overlaid by a singlethickness of tubular fabric, to cause fabric immediately adjacent theinner ring to be unsuitable as a suturing site, and to hold the foldedtubular fabric portions away from the inner ring.
 5. The valve of claim4 in which said closure member is a hollow ball.
 6. The valve of claim 5in which said ball is made of carbon.
 7. The valve of claim 5 in whichthe inner ring presents a convex curved surface along one dimension tosaid hollow ball, whereby a line contact between the ball and inner ringis effected when said ball is in flow occluding position.
 8. The valveof claim 7 having a cage for retaining said ball, said cage comprisingstruts which rest on said protrusion and which are retained between saidinner and outer rings.
 9. The valve of claim 8 in which both said innerring and ball have an outer coating of an isotropic pyrolytic carbon.